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Gonçalves YC, de Francisco Campos KC, da Silva Vasconcelos E, D'Almeida Eça BM, Rantin FT, Kalinin AL, Monteiro DA. Activation of the cannabinoid type 2 (CB2) receptor improves cardiac contractile performance in fish, Brycon amazonicus. Comp Biochem Physiol C Toxicol Pharmacol 2024; 277:109822. [PMID: 38113964 DOI: 10.1016/j.cbpc.2023.109822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/30/2023] [Accepted: 12/15/2023] [Indexed: 12/21/2023]
Abstract
In addition to their well-known classical effects, cannabinoid CB1 and CB2 receptors have also been involvement in both deleterious and protective actions on the heart under various pathological conditions. While the potential therapeutic applications of the endocannabinoid system in the context of cardiovascular function are indeed a viable prospect, significant debate exists within the literature regarding whether CB1, CB2, or a combination of both receptors exert a favorable influence on cardiac function. Hence, the aim of this study was to investigate the effects of CB1 + CB2 or CB2 agonists on cardiac excitation-contraction (E-C) coupling, utilizing fish (Brycon amazonicus) as an experimental model. The CB2 agonist elicited marked positive inotropic and lusitropic responses in isolated ventricular myocardium, induced cyclic adenosine 3',5'-monophosphate (cAMP) production, and upregulated critical Ca2+ handling proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). Our current study demonstrated, for the first time, that CB2 receptor activation-induced effects improved the efficiency of Ca2+ cycling, excitation-contraction coupling (E-C coupling), and cardiac performance in under physiological conditions. Hence, CB2 receptors could be considered a potential therapeutic target for modulating cardiac contractile dysfunctions.
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Affiliation(s)
- Yan Costa Gonçalves
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil; Joint Graduate Program in Physiological Sciences, Federal University of São Carlos (UFSCar)/São Paulo State University (UNESP), 13565-905 São Carlos, São Paulo, Brazil
| | | | - Eliton da Silva Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil
| | - Beatriz Micucci D'Almeida Eça
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil
| | - Francisco Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil
| | - Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), 13565-905 São Carlos, São Paulo, Brazil.
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2
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Smith B, Crossley DA, Wang T, Joyce W. No evidence for pericardial restraint in the snapping turtle (Chelydra serpentina) following pharmacologically-induced bradycardia at rest or during exercise. Am J Physiol Regul Integr Comp Physiol 2022; 322:R389-R399. [PMID: 35200048 PMCID: PMC9018006 DOI: 10.1152/ajpregu.00004.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Most animals elevate cardiac output during exercise through a rise in heart rate (fH), whilst stroke volume (VS) remains relatively unchanged. Cardiac pacing reveals that elevating fH alone does not alter cardiac output, which is instead largely regulated by the peripheral vasculature. In terms of myocardial oxygen demand, an increase in fH is more costly than that which would incur if VS instead were to increase. We hypothesized that fH must increase because any substantial rise in VS would be constrained by the pericardium. To investigate this hypothesis, we explored the effects of pharmacologically-induced bradycardia, with ivabradine treatment, on VS at rest and during exercise in the common snapping turtle (Chelydra serpentina) with intact or opened pericardium. We first showed that, in isolated myocardial preparations, ivabradine exerted a pronounced positive inotropic effect on atrial tissue, but only minor effects on ventricle. Ivabradine reduced fH in vivo, such that exercise tachycardia was attenuated. Pulmonary and systemic VS rose in response to ivabradine. The rise in pulmonary VS largely compensated for the bradycardia at rest, leaving total pulmonary flow unchanged by ivabradine, although ivabradine reduced pulmonary blood flow during swimming (exercise x ivabradine interaction, P<0.05). Although systemic VS increased, systemic blood flow was reduced by ivabradine both at rest and during exercise, in spite of ivabradine's potential to increase cardiac contractility. Opening the pericardium had no effect on fH, VS or blood flows before or after ivabradine, indicating that the pericardium does not constrain VS in turtles, even during pharmacologically-induced bradycardia.
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Affiliation(s)
- Brandt Smith
- Department of Biological Sciences, University of North Texas, Denton, TX, United States
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, TX, United States
| | - Tobias Wang
- Department of Biology- Zoophysiology, Aarhus University, Aarhus C, Denmark
| | - William Joyce
- Department of Biology- Zoophysiology, Aarhus University, Aarhus C, Denmark
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3
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Garner M, Stecyk JA. Does the ventricle limit cardiac contraction rate in the anoxic turtle (Trachemys scripta)? I. Comparison of the intrinsic contractile responses of cardiac chambers to the extracellular changes that accompany prolonged anoxia exposure. Curr Res Physiol 2022; 5:312-326. [PMID: 35872835 PMCID: PMC9301509 DOI: 10.1016/j.crphys.2022.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/27/2022] [Accepted: 07/04/2022] [Indexed: 11/24/2022] Open
Abstract
Multiple lines of evidence suggest that an inability of the ventricle to contract in coordination with the pacemaker during anoxia exposure may suppress cardiac pumping rate in anoxia-tolerant turtles. To determine under what extracellular conditions the ventricle could be the weak link that limits cardiac pumping, we compared, under various extracellular conditions, the intrinsic contractile properties of isometrically-contracting ventricular and atrial strips obtained from 21 °C- to 5 °C- acclimated turtles (Trachemys scripta) that had been exposed to either normoxia or anoxia (16 h at 21 °C; 12 days at 5 °C). We found that combined extracellular anoxia, acidosis, and hyperkalemia (AAK), severely disrupted ventricular, but not right or left atrial, excitability and contractibility of 5 °C anoxic turtles. However, combined hypercalcemia and heightened adrenergic stimulation counteracted the negative effects of AAK. We also report that the turtle heart is resilient to prolonged diastolic intervals, which would ensure that contractile force is maintained if arrhythmia were to occur during anoxia exposure. Finally, our findings reinforce that prior temperature and anoxia experiences are central to the intrinsic contractile response of the turtle myocardium to altered extracellular conditions. At 21 °C, prior anoxia exposure preconditioned the ventricle for anoxic and acidosis exposure. At 5 °C, prior anoxia exposure evoked heightened sensitivity of the ventricle to hyperkalemia, as well as all chambers to combined hypercalcemia and increased adrenergic stimulation. Overall, our findings show that the ventricle could limit cardiac pumping rate during prolonged anoxic submergence in cold-acclimated turtles if hypercalcemia and heightened adrenergic stimulation are insufficient to counteract the negative effects of combined extracellular anoxia, acidosis, and hyperkalemia. Turtle atria are more resilient to extracellular factors that disrupt contraction than the ventricle. Combined anoxia, acidosis, and hyperkalemia disrupted ventricular excitability and contractibility of 5 °C anoxic turtles. Heightened adrenergic stimulation counteracted the negative effects. The ventricle could limit cardiac pumping during anoxia at 5 °C if adrenergic stimulation is low.
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Monteiro DA, Lopes AG, Jejcic NU, da Silva Vasconcelos E, Kalinin AL, Rantin FT. Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca 2+, sarcoplasmic reticulum, and β-adrenergic stimulation. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1969-1982. [PMID: 34668117 DOI: 10.1007/s10695-021-01023-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
This study investigated the dependence of contraction from extracellular Ca2+, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca2+-handling proteins such as SR-Ca2+-ATPase (SERCA), phospholamban (PLN), and Na+/Ca2+ exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca2+; (2) inhibition of SR Ca2+-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca2+ content and NCX as the main pathway for Ca2+ extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.0 Hz); (5) ventricular tissue was responsive to β-adrenergic stimulation, which caused significant increases in twitch force, kept a linear force-frequency relationship from 12 to 96 bpm (0.2 to Hz), and improved the cardiac pumping capacity (CPC); and (6) African catfish myocardium exhibited similar expression patterns of NCX, SERCA, and PLN, corroborating our findings that both mechanisms for Ca2+ transport across the SR and sarcolemma contribute to Ca2+ activator. In conclusion, this fish species displays great physiological plasticity of E-C coupling, able to improve the ability to maintain cardiac performance under physiological conditions to ecological and/or adverse environmental conditions, such as hypoxic air-breathing activity.
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Affiliation(s)
- Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil.
| | - André Guelli Lopes
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Nathalia Usun Jejcic
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Eliton da Silva Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
| | - Francisco Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luís km 235, 13565-905 São Carlos, São Paulo, Brazil
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Stecyk JAW, Barber RG, Cussins J, Hall D. Indirect evidence that anoxia exposure and cold acclimation alter transarcolemmal Ca 2+ flux in the cardiac pacemaker, right atrium and ventricle of the red-eared slider turtle (Trachemys scripta). Comp Biochem Physiol A Mol Integr Physiol 2021; 261:111043. [PMID: 34332046 DOI: 10.1016/j.cbpa.2021.111043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 12/15/2022]
Abstract
We indirectly assessed if altered transarcolemmal Ca2+ flux accompanies the decreased cardiac activity displayed by Trachemys scripta with anoxia exposure and cold acclimation. Turtles were first acclimated to 21 °C or 5 °C and held under normoxic (21N; 5N) or anoxic conditions (21A; 5A). We then compared the response of intrinsic heart rate (fH) and maximal developed force of spontaneously contracting right atria (Fmax,RA), and maximal developed force of isometrically-contracting ventricular strips (Fmax,V), to Ni2+ (0.1-10 mM), which respectively blocks T-type Ca2+ channels, L-type Ca2+ channels and the Na+-Ca2+-exchanger at the low, intermediate and high concentrations employed. Dose-response curves were established in simulated in vivo normoxic (Sim Norm) or simulated in vivo anoxic extracellular conditions (Sim Anx; 21A and 5A preparations). Ni2+ decreased intrinsic fH, Fmax,RA and Fmax,V of 21N tissues in a concentration-dependent manner, but the responses were blunted in 21A tissues in Sim Norm. Similarly, dose-response curves for Fmax,RA and Fmax,V of 5N tissues were right-shifted, whereas anoxia exposure at 5 °C did not further alter the responses. The influence of Sim Anx was acclimation temperature-, cardiac chamber- and contractile parameter-dependent. Combined, the findings suggest that: (1) reduced transarcolemmal Ca2+ flux in the cardiac pacemaker is a potential mechanism underlying the slowed intrinsic fH of anoxic turtles at 21 °C, but not 5 °C, (2) a downregulation of transarcolemmal Ca2+ flux may aid cardiac anoxia survival at 21 °C and prime the turtle myocardium for winter anoxia and (3) confirm that altered extracellular conditions with anoxia exposure can modify turtle cardiac transarcolemmal Ca2+ flux.
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Affiliation(s)
- Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America.
| | - Riley G Barber
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America
| | - Jace Cussins
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America
| | - Diarmid Hall
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States of America
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6
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Lopes AG, Monteiro DA, Kalinin AL. Effects of change in temperature on the cardiac contractility of broad-snouted caiman (Caiman latirostris) during digestion. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:417-425. [PMID: 33773091 DOI: 10.1002/jez.2457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/12/2021] [Accepted: 03/13/2021] [Indexed: 11/07/2022]
Abstract
In many reptiles, digestion has been associated with the selection of higher body temperatures, the so-called post-prandial thermophilic response. This study aimed to investigate the excitation-contraction (E-C) coupling in postprandial broad-snouted caimans (Caiman latirostris) in response to acute warming within a preferred body temperature range of crocodiles. Isometric preparations subjected to a temperature transition from 25°C to 30°C were used to investigate myocardial contractility of postprandial caimans, that is, 48 h after the animals ingested a rodent meal corresponding to 15% of body mass. The caiman heart exhibits a negative force-frequency relationship that is independent of the temperature. At 25°C, cardiac muscle was able to maintain a constant force up to 36 bpm, above which it decreased significantly, reaching minimum values at the highest frequency of 84 bpm. Moreover, E-C coupling is predominantly dependent on transsarcolemmal Ca2+ transport denoted by the lack of significant ryanodine effects on force generation. On the contrary, ventricular strips at 30°C were able to sustain the cardiac contractility at higher pacing frequencies (from 12 to 144 bpm) due to an important role of Na+ /Ca2+ exchanger in Ca2+ cycling, as indicated by the decay of the post-rest contraction, and a significant contribution of the sarcoplasmic reticulum above 72 bpm. Our results demonstrated that the myocardium of postprandial caimans exhibits a significant degree of thermal plasticity of E-C coupling during acute warming. Therefore, myocardial contractility can be maximized when postprandial broad-snouted caimans select higher body temperatures (preferred temperature zone) following feeding.
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Affiliation(s)
- André G Lopes
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil.,Joint Graduate Program in Physiological Sciences, Federal University of São Carlos-UFSCar/São Paulo State University, UNESP Campus Araraquara, Araraquara, São Paulo, Brazil
| | - Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, São Paulo, Brazil
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7
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Abstract
In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, Q̇ sys) under most circumstances. Instead, Q̇ sys is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark .,Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
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8
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da Silva Vasconcelos E, Kalinin AL, Cipriano RC, Dos Santos Beserra S, Lopes AG, da Costa Leite CA, Monteiro DA. Effects of feeding and digestion on myocardial contractility and expression of calcium-handling proteins in Burmese pythons (Python molurus). Comp Biochem Physiol B Biochem Mol Biol 2019; 240:110371. [PMID: 31676333 DOI: 10.1016/j.cbpb.2019.110371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/07/2019] [Accepted: 10/14/2019] [Indexed: 12/20/2022]
Abstract
Pythons are important models of studies on postprandial metabolism because their physiological responses are exacerbated when digesting large prey. Prior studies of these animals have shown hypertrophy of the cardiac tissue 2 to 3 days after feeding, coinciding with the peak of the specific dynamic action (SDA), but the consequences of this remodeling in myocardial contractility have not been studied, which is the purpose of this work. Specimens of Python molurus were divided into two groups: a Digesting group (2 days after feeding, at the peak of SDA), and a Fasting group (28 days after feeding). When compared to the Fasting group, the Digesting group showed higher relative ventricular mass and calcium-handling protein expression such as sarcoplasmic reticulum Ca2+-ATPase (SERCA), phospholamban (PLB), and the Na+/Ca2+ exchanger (NCX). Digesting pythons also exhibited significant increases in the cardiac contraction force (Fc), rates of force development and relaxation, and cardiac pumping capacity. Therefore, the higher SERCA, PLB and NCX expression levels increased cytosolic Ca2+ transient amplitude, improving myofilament force. These changes are crucial to maintain cardiac output and a relatively high and continuous blood flow required by metabolic expenditure that occurs in postprandial animals.
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Affiliation(s)
- Eliton da Silva Vasconcelos
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Ana Lúcia Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Rafael Correa Cipriano
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | | | - André Guelli Lopes
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | | | - Diana Amaral Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil.
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9
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Joyce W, Crossley DA, Wang T, Jensen B. Smooth Muscle in Cardiac Chambers is Common in Turtles and Extensive in the Emydid Turtle, Trachemys scripta. Anat Rec (Hoboken) 2019; 303:1327-1336. [PMID: 31509333 PMCID: PMC7216914 DOI: 10.1002/ar.24257] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 06/24/2019] [Accepted: 06/28/2019] [Indexed: 02/03/2023]
Abstract
A prominent layer of smooth muscle lining the luminal side of the atria of freshwater turtles (Emydidae) was described more than a century ago. We recently demonstrated that this smooth muscle provides a previously unrecognized mechanism to change cardiac output in the emydid red-eared slider (Trachemys scripta) that possibly contributes to their tremendous diving capacity. The purpose of the present immunohistochemical study was firstly to screen major groups of vertebrates for the presence of cardiac smooth muscle. Secondly, we investigated the phylogenetic distribution of cardiac smooth muscle within the turtle order (Testudines), including terrestrial and aquatic species. Atrial smooth muscle was not detected in a range of vertebrates, including Xenopus laevis, Alligator mississippiensis, and Caiman crocodilus, all of which have pronounced diving capacities. However, we confirmed earlier reports that traces of smooth muscle are found in human atrial tissue. Only within the turtles (eight species) was there substantial amounts of nonvascular smooth muscle in the heart. This amount was greatest in the atria, while the amount in proportion to cardiac muscle was greater in the sinus venosus than in other chambers. T. scripta had more smooth muscle in the sinus venosus and atria than the other turtles. In some specimens, there was some smooth muscle in the ventricle and the pulmonary vein. Our study demonstrates that cardiac smooth muscle likely appeared early in turtle evolution and has become extensive within the Emydidae family, possibly in association with diving. Across other tetrapod clades, cardiac smooth muscle might not associate with diving. Anat Rec, 303:1327-1336, 2020. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association for Anatomy.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
| | - Dane A Crossley
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam 1105AZ, the Netherlands
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Bjarke Jensen
- Department of Medical Biology, University Medical Center Amsterdam, Amsterdam, The Netherlands
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10
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The electrocardiogram of vertebrates: Evolutionary changes from ectothermy to endothermy. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 144:16-29. [DOI: 10.1016/j.pbiomolbio.2018.08.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 08/09/2018] [Accepted: 08/13/2018] [Indexed: 12/11/2022]
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11
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Joyce W, Axelsson M, Wang T. Contraction of atrial smooth muscle reduces cardiac output in perfused turtle hearts. ACTA ACUST UNITED AC 2019; 222:jeb.199828. [PMID: 30787139 DOI: 10.1242/jeb.199828] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 02/18/2019] [Indexed: 11/20/2022]
Abstract
Unusual undulations in resting tension (tonus waves) were described in isolated atria from freshwater turtles more than a century ago. These tonus waves were soon after married with the histological demonstration of a rich layer of smooth muscle on the luminal side of the atrial wall. Research thereafter waned and the functional significance of this smooth muscle has remained obscure. Here, we provide evidence that contraction of the smooth muscle in the atria may be able to change cardiac output in turtle hearts. In in situ perfused hearts of the red-eared slider turtle (Trachemys scripta elegans), we demonstrated that activation of smooth muscle contraction with histamine (100 nmol kg-1 bolus injected into perfusate) reduced cardiac output by decreasing stroke volume (>50% decrease in both parameters). Conversely, inhibition of smooth muscle contraction with wortmannin (10 µmol l-1 perfusion) approximately doubled baseline stroke volume and cardiac output. We suggest that atrial smooth muscle provides a unique mechanism to control cardiac filling that could be involved in the regulation of stroke volume during diving.
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Affiliation(s)
- William Joyce
- Department of Bioscience, Section for Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE 405 30 Gothenburg, Sweden
| | - Tobias Wang
- Department of Bioscience, Section for Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark.,Aarhus Institute of Advanced Studies, Aarhus University, 8000 Aarhus C, Denmark
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12
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Fanter CE, Lin Z, Keenan SW, Janzen FJ, Mitchell TS, Warren DE. Development-specific transcriptomic profiling suggests new mechanisms for anoxic survival in the ventricle of overwintering turtles. J Exp Biol 2019; 223:jeb.213918. [DOI: 10.1242/jeb.213918] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 12/18/2019] [Indexed: 12/28/2022]
Abstract
Oxygen deprivation swiftly damages tissues in most animals, yet some species show remarkable abilities to tolerate little or even no oxygen. Painted turtles exhibit a development-dependent tolerance that allows adults to survive anoxia ∼4x longer than hatchlings: adults survive ∼170 days and hatchlings survive ∼40 days at 3°C. We hypothesized this difference is related to development-dependent differences in ventricular gene expression. Using a comparative ontogenetic approach, we examined whole transcriptomic changes before, during, and five days after a 20-day bout of anoxic submergence at 3°C. Ontogeny accounted for more gene expression differences than treatment (anoxia or recovery): 1,175 vs. 237 genes, respectively. Of the 237 differences, 93 could confer protection against anoxia and reperfusion injury, 68 could be injurious, and 20 may be constitutively protective. Especially striking during anoxia was the expression pattern of all 76 annotated ribosomal protein (R-protein) mRNAs, which decreased in anoxia-tolerant adults, but increased in anoxia-sensitive hatchlings, suggesting adult-specific regulation of translational suppression. These genes, along with 60 others that decreased their levels in adults and either increased or remained unchanged in hatchlings, implicate antagonistic pleiotropy as a mechanism to resolve the long-standing question about why hatchling painted turtles overwinter in terrestrial nests, rather than emerge and overwinter in water during their first year. In sum, developmental differences in the transcriptome of the turtle ventricle revealed potentially protective mechanisms that contribute to extraordinary adult-specific anoxia tolerance, and provide a unique perspective on differences between the anoxia-induced molecular responses of anoxia-tolerant or anoxia-sensitive phenotypes within a species.
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Affiliation(s)
- Cornelia E. Fanter
- Saint Louis University, Department of Biology, 3507 Laclede Ave., St. Louis, Missouri, 63103, USA
| | - Zhenguo Lin
- Saint Louis University, Department of Biology, 3507 Laclede Ave., St. Louis, Missouri, 63103, USA
| | - Sarah W. Keenan
- South Dakota School of Mines & Technology, Department of Geology and Geological Engineering, 501 East St. Joseph St., Rapid City, South Dakota, 57701, USA
| | - Fredric J. Janzen
- Iowa State University, Department of Ecology, Evolution and Organismal Biology, 251 Bessey Hall, Ames, Iowa, 50011, USA
| | - Timothy S. Mitchell
- University of Minnesota, Department of Ecology, Evolution and Behavior, 1479 Gortner Ave. Saint Paul, MN, 55108, USA
| | - Daniel E. Warren
- Saint Louis University, Department of Biology, 3507 Laclede Ave., St. Louis, Missouri, 63103, USA
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13
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Fanter CE, Campbell KS, Warren DE. The effects of pH and P i on tension and Ca 2+ sensitivity of ventricular myofilaments from the anoxia-tolerant painted turtle. ACTA ACUST UNITED AC 2017; 220:4234-4241. [PMID: 28939564 DOI: 10.1242/jeb.164137] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 09/17/2017] [Indexed: 11/20/2022]
Abstract
We aimed to determine how increases in intracellular H+ and inorganic phosphate (Pi) to levels observed during anoxic submergence affect contractility in ventricular muscle of the anoxia-tolerant Western painted turtle, Chrysemys picta bellii Skinned multicellular preparations were exposed to six treatments with physiologically relevant levels of pH (7.4, 7.0, 6.6) and Pi (3 and 8 mmol l-1). Each preparation was tested in a range of calcium concentrations (pCa 9.0-4.5) to determine the pCa-tension relationship for each treatment. Acidosis significantly decreased contractility by decreasing Ca2+ sensitivity (pCa50) and tension development (P<0.001). Increasing [Pi] also decreased contractility by decreasing tension development at every pH level (P<0.001) but, alone, did not affect Ca2+ sensitivity (P=0.689). Simultaneous increases in [H+] and [Pi] interacted to attenuate the decreased tension development and Ca2+ sensitivity (P<0.001), possibly reflecting a decreased sensitivity to Pi when it is present as the dihydrogen phosphate form, which increases as pH decreases. Compared with that of mammals, the ventricle of turtles exhibits higher Ca2+ sensitivity, which is consistent with previous studies of ectothermic vertebrates.
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Affiliation(s)
- Cornelia E Fanter
- Department of Biology, Saint Louis University, St Louis, MO 63109, USA
| | - Kenneth S Campbell
- University of Kentucky, Department of Physiology and Division of Cardiovascular Medicine, Lexington, KY 40536, USA
| | - Daniel E Warren
- Department of Biology, Saint Louis University, St Louis, MO 63109, USA
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14
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Larsen J, Bushnell P, Steffensen J, Pedersen M, Qvortrup K, Brill R. Characterization of the functional and anatomical differences in the atrial and ventricular myocardium from three species of elasmobranch fishes: smooth dogfish (Mustelus canis), sandbar shark (Carcharhinus plumbeus), and clearnose skate (Raja eglanteria). J Comp Physiol B 2016; 187:291-313. [PMID: 27686667 DOI: 10.1007/s00360-016-1034-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 08/25/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
We assessed the functional properties in atrial and ventricular myocardium (using isolated cardiac strips) of smooth dogfish (Mustelus canis), clearnose skate (Raja eglanteria), and sandbar shark (Carcharhinus plumbeus) by blocking Ca2+ release from the sarcoplasmic reticulum (SR) with ryanodine and thapsigargin and measuring the resultant changes in contraction-relaxation parameters and the force-frequency relationship at 20 °C and 30 °C. We also examined ultrastructural differences with electron microscopy. In tissues from smooth dogfish, net force (per cross-sectional area) and measures of the speeds of contraction and relaxation were all higher in atrial than ventricular myocardium at both temperatures. Atrial-ventricular differences were evident in the other two species primarily in measures of the rates of contraction and relaxation. Ryanodine-thapsigargin treatment reduced net force and its maximum positive first derivative (i.e., contractility), and increased time to 50 % relaxation in atrial tissue from smooth dogfish at 30 °C. It also increased times to peak force and half relaxation in clearnose skate atrial and ventricular tissue at both temperatures, but only in atrial tissue from sandbar shark at 30 °C; indicating that SR involvement in excitation-contraction (EC) coupling is species- and temperature-specific in elasmobranch fishes, as it is in teleost fishes. Atrial and ventricular myocardium from all three species displayed a negative force-frequency relationship, but there was no evidence that SR involvement in EC coupling was influenced by heart rate. SR was evident in electron micrographs, generally located in proximity to mitochondria and intercalated discs, and to a lesser extent between the myofibrils; with mitochondria being more numerous in ventricular than atrial myocardium in all three species.
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Affiliation(s)
- Julie Larsen
- Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000, Helsingør, Denmark
| | - Peter Bushnell
- Department of Biology, Indiana University South Bend, 1700 Mishawaka Avenue, South Bend, IN, 46634-7111, USA
| | - John Steffensen
- Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000, Helsingør, Denmark
| | - Morten Pedersen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark
| | - Klaus Qvortrup
- Department of Biomedical Sciences/CFIM, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen, Denmark
| | - Richard Brill
- Behavioral Ecology Branch, Ecosystems Processes Division, Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, Sandy Hook, NJ, USA. .,Virginia Institute of Marine Science, PO Box 1346, Gloucester Point, VA, 23062, USA.
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15
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Joyce W, Axelsson M, Wang T. Autoregulation of cardiac output is overcome by adrenergic stimulation in the anaconda heart. J Exp Biol 2016; 220:336-340. [DOI: 10.1242/jeb.149237] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 11/03/2016] [Indexed: 11/20/2022]
Abstract
Most vertebrates increase cardiac output during activity by elevating heart rate with relatively stable stroke volume. However, several studies have demonstrated ‘intrinsic autoregulation’ of cardiac output where artificially increased heart rate is associated with decreased stroke volume, leaving cardiac output unchanged. We explored the capacity of noradrenaline to overcome autoregulation in the anaconda heart. Electrically pacing in situ perfused hearts from the intrinsic heart rate to the maximum attainable resulted in a proportional decrease in stroke volume. However, noradrenaline, which increased heart rate to the same frequency as pacing, maintained stroke volume and thus increased cardiac output. In atrial and ventricular preparations noradrenaline significantly increased the force of contraction and contraction kinetics. Thus, the increased contractility associated with adrenergic stimulation ameliorates filling limitations at high heart rates. Although heart rate appears the primary regulated variable during activity, this may only be achieved with compensatory amendments in myocardial contractility provided by adrenergic stimulation.
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Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Tobias Wang
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
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16
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Germer CM, Tomaz JM, Carvalho AF, Bassani RA, Bassani JWM. Electrocardiogram, heart movement and heart rate in the awake gecko (Hemidactylus mabouia). J Comp Physiol B 2014; 185:111-8. [DOI: 10.1007/s00360-014-0873-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 10/22/2014] [Accepted: 11/04/2014] [Indexed: 10/24/2022]
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17
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Shiels HA, Galli GL. The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart. Physiology (Bethesda) 2014; 29:456-69. [DOI: 10.1152/physiol.00015.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The sarcoplasmic reticulum (SR) is crucial for contraction and relaxation of the mammalian cardiomyocyte, but its role in other vertebrate classes is equivocal. Recent evidence suggests differences in SR function across species may have an underlying structural basis. Here, we discuss how SR recruitment relates to the structural organization of the cardiomyocyte to provide new insight into the evolution of cardiac design and function in vertebrates.
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Affiliation(s)
- Holly A. Shiels
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom; and
| | - Gina L.J. Galli
- Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom
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18
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Joyce W, Gesser H, Wang T. Purinoceptors exert negative inotropic effects on the heart in all major groups of reptiles. Comp Biochem Physiol A Mol Integr Physiol 2014; 171:16-22. [PMID: 24521885 DOI: 10.1016/j.cbpa.2014.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 02/02/2014] [Accepted: 02/04/2014] [Indexed: 01/23/2023]
Abstract
The few and fragmentary studies on purinergic regulation of the reptile heart have reached equivocal conclusions. Indeed, unlike fish, amphibians, and mammals, it has been suggested that the turtle heart lacks purinoceptors. Here, we study the effect of adenosine and ATP on isolated heart strips from three species of reptiles: the red-eared slider (Trachemys scripta), the ball python (Python regius) and the spectacled caiman (Caiman crocodilus). Both adenosine and ATP markedly decreased contractility in atria from all three species. This was attenuated by theophylline, suggesting that the response is mediated by P1 receptors. Ventricles were less sensitive, although high concentrations of the adenyl compounds evoked decreases in contractility. Our study suggests that cardiac purinoceptors are ubiquitous across reptiles, and may play an important and underappreciated role in reptile cardiovascular physiology.
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Affiliation(s)
- William Joyce
- Zoophysiology, Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark; Faculty of Life Sciences, The University of Manchester, M13 9PT, UK.
| | - Hans Gesser
- Zoophysiology, Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Tobias Wang
- Zoophysiology, Department of Biosciences, Aarhus University, DK-8000 Aarhus C, Denmark
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19
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Jensen B, Moorman AFM, Wang T. Structure and function of the hearts of lizards and snakes. Biol Rev Camb Philos Soc 2013; 89:302-36. [DOI: 10.1111/brv.12056] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 06/26/2013] [Accepted: 07/30/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Bjarke Jensen
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Antoon F. M. Moorman
- Department of Anatomy, Embryology & Physiology, Academic Medical Center; University of Amsterdam; Amsterdam 1105 The Netherlands
| | - Tobias Wang
- Department of Bioscience, Zoophysiology; Aarhus University; Aarhus C 8000 Denmark
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20
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da Silveira LC, do Nascimento LFR, Colquhoun A, Abe AS, de Souza SCR. Cardiac hypertrophy and structural and metabolic remodeling related to seasonal dormancy in the first annual cycle in tegu lizards. Comp Biochem Physiol A Mol Integr Physiol 2013; 165:371-80. [PMID: 23603066 DOI: 10.1016/j.cbpa.2013.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/09/2013] [Accepted: 04/11/2013] [Indexed: 11/16/2022]
Abstract
Morpho-functional adjustments in the heart of juvenile tegu lizards (Tupinambis merianae) were analyzed at distinct seasonal periods to investigate how the demands of growth and of energy saving are reconciled during the first annual cycle. The relative ventricular mass (Mv) was 31% and 69% larger in late autumn and winter dormancy, respectively, compared to early autumn. This effect did not persist during unfed arousal, suggesting that protein accumulates in the heart during hypometabolism and is degraded on arousal. Both the hypertrophy and the atrophy were disproportionate in the largest individuals. In contrast, Mv was smaller in lizards that were starved during spring activity compared to fed lizards, this effect being larger in smaller individuals. In late autumn and winter dormancy the spongy myocardium had 8% of the section area covered by lacunary spaces, which expanded after food intake during arousal and reached 29% in spring activity together with higher density of cardiomyocytes. Total and soluble proteins per mass unity were unchanged, and maximum activities of selected enzymes suggest sustained glycolytic and aerobic capacities during hypometabolism. Results indicate that important structural adjustments occur in the heart in anticipation of dormancy, and that the protein balance in the tissue is maintained at winter temperatures ~17°C.
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21
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Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012; 205:9-25. [PMID: 22463608 DOI: 10.1111/j.1748-1716.2012.02389.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phospholamban (PLN) is a small phosphoprotein closely associated with the cardiac sarcoplasmic reticulum (SR). Dephosphorylated PLN tonically inhibits the SR Ca-ATPase (SERCA2a), while phosphorylation at Ser16 by PKA and Thr17 by Ca(2+) /calmodulin-dependent protein kinase (CaMKII) relieves the inhibition, and this increases SR Ca(2+) uptake. For this reason, PLN is one of the major determinants of cardiac contractility and relaxation. In this review, we attempted to highlight the functional significance of PLN in vertebrate cardiac physiology. We will refer to the huge literature on mammals in order to describe the molecular characteristics of this protein, its interaction with SERCA2a and its role in the regulation of the mechanic and the electric performance of the heart under basal conditions, in the presence of chemical and physical stresses, such as β-adrenergic stimulation, response to stretch, force-frequency relationship and intracellular acidosis. Our aim is to provide the basis to discuss the role of PLN also on the cardiac function of nonmammalian vertebrates, because so far this aspect has been almost neglected. Accordingly, when possible, the literature on PLN will be analysed taking into account the nonuniform cardiac structural and functional characteristics encountered in ectothermic vertebrates, such as the peculiar and variable organization of the SR, the large spectrum of response to stresses and the disaptive absence of crucial proteins (i.e. haemoglobinless and myoglobinless species).
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Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
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22
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Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012. [DOI: 10.1111/j.1748-1716.2011.02389.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
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23
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Warren DE, Galli GLJ, Patrick SM, Shiels HA. The cellular force-frequency response in ventricular myocytes from the varanid lizard, Varanus exanthematicus. Am J Physiol Regul Integr Comp Physiol 2010; 298:R567-74. [PMID: 20053961 DOI: 10.1152/ajpregu.00650.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate the cellular mechanisms underlying the negative force-frequency relationship (FFR) in the ventricle of the varanid lizard, Varanus exanthematicus, we measured sarcomere and cell shortening, intracellular Ca(2+) ([Ca(2+)](i)), action potentials (APs), and K(+) currents in isolated ventricular myocytes. Experiments were conducted between 0.2 and 1.0 Hz, which spans the physiological range of in vivo heart rates at 20-22 degrees C for this species. As stimulation frequency increased, diastolic length, percent change in sarcomere length, and relaxation time all decreased significantly. Shortening velocity was unaffected. These changes corresponded to a faster rate of rise of [Ca(2+)](i), a decrease in [Ca(2+)](i) transient amplitude, and a seven-fold increase in diastolic [Ca(2+)](i). The time constant for the decay of the Ca(2+) transient (tau) decreased at higher frequencies, indicating a frequency-dependent acceleration of relaxation (FDAR) but then reached a plateau at moderate frequencies and did not change above 0.5 Hz. The rate of rise of the AP was unaffected, but the AP duration (APD) decreased with increasing frequency. Peak depolarization tended to decrease, but it was only significant at 1.0 Hz. The decrease in APD was not due to frequency-dependent changes in the delayed inward rectifier (I(Kr)) or the transient outward (I(to)) current, as neither appeared to be present in varanid ventricular myocytes. Our results suggest that a negative FFR relationship in varanid lizard ventricle is caused by decreased amplitude of the Ca(2+) transient coupled with an increase in diastolic Ca(2+), which leads to incomplete relaxation between beats at high frequencies. This coincides with shortened APD at higher frequencies.
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Affiliation(s)
- Daniel E Warren
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94143, USA.
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24
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Guo Z, Wang S, Jiao Q, Xu M, Gao F. RNAi targeting ryanodine receptor 2 protects rat cardiomyocytes from injury caused by simulated ischemia-reperfusion. Biomed Pharmacother 2009; 64:184-90. [PMID: 20053523 DOI: 10.1016/j.biopha.2009.09.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022] Open
Abstract
The effects of a small interfering RNA targeting ryanodine receptor 2 (si-Ryr2) on cardiomyocytes injury following a simulated ischemia-reperfusion (I/R) were investigated. Pretreated with si-Ryr2 or ryanodine, primary cultures of neonatal rat cardiomyocytes were subjected to a protocol of simulated I/R. Compared with control, the cytosolic Ca(2+) concentration ([Ca(2+)](i)) and the generation of reactive oxygen species (ROS) was significantly augmented after I/R. Concomitant with these, cell injury assessed by Annexin V/PI staing, mitochondria membrane potential (DeltaPsim) and the leakage of lactic dehydrogenase (LDH) and creatine phosphokinase (CPK) were aggravated. Si-Ryr2 treatment reduced [Ca(2+)](i) and ROS generation and protected the cardiomyocytes from subsequent I/R injury, as evidenced by stable DeltaPsim and decreased Annexin V(+) PI(-) staing and enzymes release. Moreover, si-Ryr2 exerted more effective protection on I/R injury compared to ryanodine. The present study demonstrated for the first time that in neonatal cardiomyocytes, si-Ryr2 reduces cell death associated with attenuating [Ca(2+)](i) and ROS production. Furthermore, we attempt to speculate that si-Ryr2 excel ryanodine in Ryr2 function research of cardioprotection.
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Affiliation(s)
- Zhuying Guo
- Experimental Center, No. 3 People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine, No. 280 Mohe Road, Baoshan District, Shanghai, China.
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25
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Galli GLJ, Warren DE, Shiels HA. Ca2+ cycling in cardiomyocytes from a high-performance reptile, the varanid lizard (Varanus exanthematicus). Am J Physiol Regul Integr Comp Physiol 2009; 297:R1636-44. [PMID: 19812356 PMCID: PMC2803631 DOI: 10.1152/ajpregu.00381.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The varanid lizard possesses one of the largest aerobic capacities among reptiles with maximum rates of oxygen consumption that are twice that of other lizards of comparable sizes at the same temperature. To support this aerobic capacity, the varanid heart possesses morphological adaptations that allow the generation of high heart rates and blood pressures. Specializations in excitation-contraction coupling may also contribute to the varanids superior cardiovascular performance. Therefore, we investigated the electrophysiological properties of the l-type Ca(2+) channel and the Na(+)/Ca(2+) exchanger (NCX) and the contribution of the sarcoplasmic reticulum to the intracellular Ca(2+) transient (Delta[Ca(2+)](i)) in varanid lizard ventricular myocytes. Additionally, we used confocal microscopy to visualize myocytes and make morphological measurements. Lizard ventricular myocytes were found to be spindle-shaped, lack T-tubules, and were approximately 190 microm in length and 5-7 microm in width and depth. Cardiomyocytes had a small cell volume ( approximately 2 pL), leading to a large surface area-to-volume ratio (18.5), typical of ectothermic vertebrates. The voltage sensitivity of the l-type Ca(2+) channel current (I(Ca)), steady-state activation and inactivation curves, and the time taken for recovery from inactivation were also similar to those measured in other reptiles and teleosts. However, transsarcolemmal Ca(2+) influx via reverse mode Na(+)/Ca(2+) exchange current was fourfold higher than most other ectotherms. Moreover, pharmacological inhibition of the sarcoplasmic reticulum led to a 40% reduction in the Delta[Ca(2+)](i) amplitude, and slowed the time course of decay. In aggregate, our results suggest varanids have an enhanced capacity to transport Ca(2+) through the Na(+)/Ca(2+) exchanger, and sarcoplasmic reticulum suggesting specializations in excitation-contraction coupling may provide a means to support high cardiovascular performance.
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Affiliation(s)
- Gina L J Galli
- Faculty of Life Sciences, The University of Manchester, Core Technology Facility, Manchester, United Kingdom.
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26
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Quindry JC. Editorial Focus: Cardiac function of the lizard king: focus on "Ca2+ cycling in cardiomyocytes from a high-performance reptile, the varanid lizard (Varanus exanthematicus)". Am J Physiol Regul Integr Comp Physiol 2009; 297:R1635. [PMID: 19793951 DOI: 10.1152/ajpregu.00618.2009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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27
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Stecyk JAW, Bock C, Overgaard J, Wang T, Farrell AP, Pörtner HO. Correlation of cardiac performance with cellular energetic components in the oxygen-deprived turtle heart. Am J Physiol Regul Integr Comp Physiol 2009; 297:R756-68. [PMID: 19587113 DOI: 10.1152/ajpregu.00102.2009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relationship between cardiac energy metabolism and the depression of myocardial performance during oxygen deprivation has remained enigmatic. Here, we combine in vivo (31)P-NMR spectroscopy and MRI to provide the first temporal profile of in vivo cardiac energetics and cardiac performance of an anoxia-tolerant vertebrate, the freshwater turtle (Trachemys scripta) during long-term anoxia exposure (approximately 3 h at 21 degrees C and 11 days at 5 degrees C). During anoxia, phosphocreatine (PCr), unbound levels of inorganic phosphate (effective P(i)(2-)), intracellular pH (pH(i)), and free energy of ATP hydrolysis (dG/dxi) exhibited asymptotic patterns of change, indicating that turtle myocardial high-energy phosphate metabolism and energetic state are reset to new, reduced steady states during long-term anoxia exposure. At 21 degrees C, anoxia caused a reduction in pH(i) from 7.40 to 7.01, a 69% decrease in PCr and a doubling of effective P(i)(2-). ATP content remained unchanged, but the free energy of ATP hydrolysis (dG/dxi) decreased from -59.6 to -52.5 kJ/mol. Even so, none of these cellular changes correlated with the anoxic depression of cardiac performance, suggesting that autonomic cardiac regulation may override putative cellular feedback mechanisms. In contrast, during anoxia at 5 degrees C, when autonomic cardiac control is severely blunted, the decrease of pH(i) from 7.66 to 7.12, 1.9-fold increase of effective P(i)(2-), and 6.4 kJ/mol decrease of dG/dxi from -53.8 to -47.4 kJ/mol were significantly correlated to the anoxic depression of cardiac performance. Our results provide the first evidence for a close, long-term coordination of functional cardiac changes with cellular energy status in a vertebrate, with a potential for autonomic control to override these immediate relationships.
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Affiliation(s)
- Jonathan A W Stecyk
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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28
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Galli GLJ, Shiels HA, Brill RW. Temperature sensitivity of cardiac function in pelagic fishes with different vertical mobilities: yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus), mahimahi (Coryphaena hippurus), and swordfish (Xiphias gladius). Physiol Biochem Zool 2009; 82:280-90. [PMID: 19284308 DOI: 10.1086/597484] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We measured the temperature sensitivity, adrenergic sensitivity, and dependence on sarcoplasmic reticulum (SR) Ca(2+) of ventricular muscle from pelagic fishes with different vertical mobility patterns: bigeye tuna (Thunnus obesus), yellowfin tuna (Thunnus albacares), and mahimahi (Coryphaena hippurus) and a single specimen from swordfish (Xiphias gladius). Ventricular muscle from the bigeye tuna and mahimahi exhibited a biphasic response to an acute decrease in temperature (from 26 degrees to 7 degrees C); twitch force and kinetic parameters initially increased and then declined. The magnitude of this response was larger in the bigeye tuna than in the mahimahi. Under steady state conditions at 26 degrees C, inhibition of SR Ca(2+) release and reuptake with ryanodine and thapsigargin decreased twitch force and kinetic parameters, respectively, in the bigeye tuna only. However, the initial inotropy associated with decreasing temperature was abolished by SR inhibition in both the bigeye tuna and the mahimahi. Application of adrenaline completely reversed the effects of ryanodine and thapsigargin, but this effect was diminished at cold temperatures. In the yellowfin tuna, temperature and SR inhibition had minor effects on twitch force and kinetics, while adrenaline significantly increased these parameters. Limited data suggest that swordfish ventricular muscle responds to acute temperature reduction, SR inhibition, and adrenergic stimulation in a manner similar to that of bigeye tuna ventricular muscle. In aggregate, our results show that the temperature sensitivity, SR dependence, and adrenergic sensitivity of pelagic fish hearts are species specific and that these differences reflect species-specific vertical mobility patterns.
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Affiliation(s)
- Gina L J Galli
- Faculty of Life Sciences, University of Manchester, Core Technology Facility, 46 Grafton Street, Manchester M13 9NT, United Kingdom.
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29
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Stecyk JAW, Galli GL, Shiels HA, Farrell AP. Cardiac survival in anoxia-tolerant vertebrates: An electrophysiological perspective. Comp Biochem Physiol C Toxicol Pharmacol 2008; 148:339-54. [PMID: 18589002 DOI: 10.1016/j.cbpc.2008.05.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 05/31/2008] [Accepted: 05/31/2008] [Indexed: 11/24/2022]
Abstract
Certain vertebrates, such as freshwater turtles of the genus Chrysemys and Trachemys and crucian carp (Carassius carassius), have anoxia-tolerant hearts that continue to function throughout prolonged periods of anoxia (up to many months) due to successful balancing of cellular ATP supply and demand. In the present review, we summarize the current and limited understanding of the cellular mechanisms underlying this cardiac anoxia tolerance. What emerges is that cold temperature substantially modifies cardiac electrophysiology to precondition the heart for winter anoxia. Intrinsic heart rate is slowed and density of sarcolemmal ion currents substantially modified to alter cardiac action potential (AP) characteristics. These changes depress cardiac activity and reduce the energetic costs associated with ion pumping. In contrast, anoxia per se results in limited changes to cardiac AP shape or ion current densities in turtle and crucian carp, suggesting that anoxic modifications of cardiac electrophysiology to reduce ATP demand are not extensive. Additionally, as knowledge of cellular physiology in non-mammalian vertebrates is still in its infancy, we briefly discuss the cellular defense mechanisms towards the acidosis that accompanies anoxia as well as mammalian cardiac models of hypoxia/ischemia tolerance. By examining if fundamental cellular mechanisms have been conserved during the evolution of anoxia tolerance we hope to have provided a framework for the design of future experiments investigating cardiac cellular mechanisms of anoxia survival.
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Affiliation(s)
- Jonathan A W Stecyk
- Physiology Programme, Department of Molecular Biosciences, University of Oslo, PO Box 1041, N-0316, Oslo, Norway.
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30
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Overgaard J, Gesser H, Wang T. Tribute to P. L. Lutz: cardiac performance and cardiovascular regulation during anoxia/hypoxia in freshwater turtles. ACTA ACUST UNITED AC 2008; 210:1687-99. [PMID: 17488932 DOI: 10.1242/jeb.001925] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Freshwater turtles overwintering in ice-covered ponds in North America may be exposed to prolonged anoxia, and survive this hostile environment by metabolic depression. Here, we review their cardiovascular function and regulation, with particular emphasis on the factors limiting cardiac performance. The pronounced anoxia tolerance of the turtle heart is based on the ability to match energy consumption with the low anaerobic ATP production during anoxia. Together with a well-developed temporal and spatial energy buffering by creatine kinase, this allows for cellular energy charge to remain high during anoxia. Furthermore, the turtle heart is well adapted to handle the adverse effects of free phosphate arising when phosphocreatine stores are used. Anoxia causes tenfold reductions in heart rate and blood flows that match the metabolic depression, and blood pressure is largely maintained through increased systemic vascular resistance. Depression of the heart rate is not driven by the autonomic nervous system and seems to arise from direct effects of oxygen lack and the associated hyperkalaemia and acidosis on the cardiac pacemaker. These intra- and extracellular changes also affect cardiac contractility, and both acidosis and hyperkalaemia severely depress cardiac contractility. However, increased levels of adrenaline and calcium may, at least partially, salvage cardiac function under prolonged periods of anoxia.
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Affiliation(s)
- Johannes Overgaard
- National Environmental Research Institute, Aarhus University, Silkeborg, Denmark
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Stecyk JAW, Paajanen V, Farrell AP, Vornanen M. Effect of temperature and prolonged anoxia exposure on electrophysiological properties of the turtle (Trachemys scripta) heart. Am J Physiol Regul Integr Comp Physiol 2007; 293:R421-37. [PMID: 17442785 DOI: 10.1152/ajpregu.00096.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac activity of the turtle (Trachemys scripta) is greatly depressed with cold acclimation and anoxia. We examined what electrophysiological modifications accompany and perhaps facilitate this depression of cardiac activity. Turtles were first acclimated to 21 degrees C or 5 degrees C and held under either normoxic or anoxic (6 h at 21 degrees C; 14 days at 5 degrees C) conditions. We then measured cardiac action potentials (APs) using spontaneously contracting whole heart preparations and whole cell current densities of sarcolemmal ion channels using isolated ventricular myocytes under appropriate normoxic and anoxic conditions. Compared with 21 degrees C-acclimated turtles, 5 degrees C-acclimated turtles exhibited a less negative resting membrane potential (by 18-29 mV), a 4.7- to 6.8-fold slower AP upstroke rate, and a 4.2- to 4.9-fold greater AP duration. Correspondingly, peak densities of ventricular voltage-gated Na(+) (I(Na)) and L-type Ca(2+) currents and inward slope conductances of inward rectifier K(+) (I(K1)) channel current were approximately 1/7th (Q(10) = 3.4), 1/13th (Q(10) = 5.0), and one-half (Q(10) = 1.4) of those of 21 degrees C-acclimated ventricular myocytes, respectively. With anoxia at 21 degrees C, peak I(Na) density doubled and ventricular AP duration increased by 47%, a change proportional to the reported approximately 30% reduction of intrinsic heart rate. In contrast, with anoxia at 5 degrees C, ventricular AP characteristics were unaffected; of the ion currents investigated, only the inward conductance via I(K1) changed significantly (reduced by 46%). The present findings indicate that cold temperature, more so than prolonged anoxia, results in substantial modifications of cardiac APs and reduction of ventricular ion current densities. These changes likely prepare cardiac muscle for winter anoxia conditions.
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Affiliation(s)
- Jonathan A W Stecyk
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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Galli GLJ, Taylor EW, Shiels HA. Calcium flux in turtle ventricular myocytes. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1781-9. [PMID: 16887918 DOI: 10.1152/ajpregu.00421.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relative contribution of the sarcoplasmic reticulum (SR), the L-type Ca2+channel and the Na+/Ca2+exchanger (NCX) were assessed in turtle ventricular myocytes using epifluorescent microscopy and electrophysiology. Confocal microscopy images of turtle myocytes revealed spindle-shaped cells, which lacked T-tubules and had a large surface area-to-volume ratio. Myocytes loaded with the fluorescent Ca2+-sensitive dye Fura-2 elicited Ca2+transients, which were insensitive to ryanodine and thapsigargin, indicating the SR plays a small role in the regulation of contraction and relaxation in the turtle ventricle. Sarcolemmal Ca2+currents were measured using the perforated-patch voltage-clamp technique. Depolarizing voltage steps to 0 mV elicited an inward current that could be blocked by nifedipine, indicating the presence of Ca2+currents originating from L-type Ca2+channels (ICa). The density of ICawas 3.2 ± 0.5 pA/pF, which led to an overall total Ca2+influx of 64.1 ± 9.3 μM/l. NCX activity was measured as the Ni+-sensitive current at two concentrations of intracellular Na+(7 and 14 mM). Total Ca2+influx through the NCX during depolarizing voltage steps to 0 mV was 58.5 ± 7.7 μmol/l and 26.7 ± 3.2 μmol/l at 14 and 7 mM intracellular Na+, respectively. In the absence of the SR and L-type Ca2+channels, the NCX is able to support myocyte contraction independently. Our results indicate turtle ventricular myocytes are primed for sarcolemmal Ca2+transport, and most of the Ca2+used for contraction originates from the L-type Ca2+channel.
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Affiliation(s)
- Gina L J Galli
- Faculty of Life Sciemces, The University of Manchester, Core Technology Facility, 46 Grafton Street, Manchester, M13 9NT UK.
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